An acceleration detection element has been proposed, which includes a movable portion over a support substrate, the movable portion being separated from the support substrate by a predetermined distance and capable of rotation (seesaw motion) in accordance with acceleration in a normal direction to a surface direction of the support substrate (refer to, for example, Patent Literature 1).
Specifically, in such an acceleration detection element, the movable portion includes a frame portion having a rectangular shape formed with an opening inside, and a torsion beam that is provided in the frame portion so as to divide the opening, and becomes a rotational axis at the time of rotation of the movable portion. The torsion beam is supported on the support substrate via an anchor portion, to be provided over the support substrate. Further, the frame portion is formed in an asymmetrical shape with respect to the torsion beam, such that the frame portion (movable portion) can rotate about the torsion beam serving as the rotational axis upon application of the acceleration in the normal direction to the surface direction of the support substrate. In detail, when one site formed by division by the torsion beam is referred to as a first site and the other site is referred to as a second site, a length (first length) from the torsion beam to the end of the first site on the opposite side to the torsion beam side is made longer than a length (second length) from the torsion beam to the end of the second site on the opposite side to the torsion beam side. That is, a mass of the first site is made larger than a mass of the second site in the frame portion.
Further, the support substrate is provided with a fixed electrode that constitutes a predetermined capacitance together with the first site, and a fixed electrode that constitutes a predetermined capacitance together with the second site. That is, the first site and the second site function as movable electrodes.
The acceleration detection element as thus described is disposed on one surface of a mount member such that the surface direction of the support substrate is parallel to the surface direction of the mount member, to thereby constitute an acceleration sensor. When acceleration is applied in a normal direction to the surface direction of the one surface of the mount member (one surface of the support substrate), the movable portion rotates about the torsion beam serving as the rotational axis. Therefore, a capacitance between the movable portion and the fixed electrode changes in accordance with the acceleration. Accordingly, the acceleration in the normal direction to the one surface of the mount member is detected by detecting a change in capacitance.